| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 11° | 0.5° | 129.4mm | 10 | 49 |
| February | 13.3° | 2.2° | 136.1mm | 10.3 | 58 |
| March | 17.7° | 5.9° | 115.2mm | 9.6 | 73 |
| April | 22.2° | 10.2° | 135.2mm | 9.3 | 81 |
| May | 26.3° | 15.5° | 120mm | 9.6 | 81 |
| June | 30.3° | 19.6° | 105.8mm | 9.4 | 68 |
| July | 31.3° | 21.6° | 141.7mm | 10.5 | 62 |
| August | 31.3° | 21.3° | 101.4mm | 8.5 | 66 |
| September | 28.2° | 17.8° | 98.8mm | 6.7 | 82 |
| October | 23° | 11.2° | 75.1mm | 5.8 | 88 |
| November | 17.3° | 5° | 104.1mm | 7.7 | 76 |
| December | 12.6° | 1.8° | 153.3mm | 10.4 | 55 |
January in Decatur averages a daily high of 11°C with nights around 0.5°C. Expect roughly 10 wet days totalling 129.4mm. Demanding conditions — pack for it and plan indoor options.
February in Decatur averages a daily high of 13.3°C with nights around 2.2°C. Expect roughly 10.3 wet days totalling 136.1mm. Generally workable, with some weather to plan around.
March in Decatur averages a daily high of 17.7°C with nights around 5.9°C. Expect roughly 9.6 wet days totalling 115.2mm. Generally workable, with some weather to plan around.
April in Decatur averages a daily high of 22.2°C with nights around 10.2°C. Expect roughly 9.3 wet days totalling 135.2mm. Comfortable conditions for being outdoors all day.
May in Decatur averages a daily high of 26.3°C with nights around 15.5°C. Expect roughly 9.6 wet days totalling 120mm. Comfortable conditions for being outdoors all day.
June in Decatur averages a daily high of 30.3°C with nights around 19.6°C. Expect roughly 9.4 wet days totalling 105.8mm. Generally workable, with some weather to plan around.
July in Decatur averages a daily high of 31.3°C with nights around 21.6°C. Expect roughly 10.5 wet days totalling 141.7mm. Generally workable, with some weather to plan around.
August in Decatur averages a daily high of 31.3°C with nights around 21.3°C. Expect roughly 8.5 wet days totalling 101.4mm. Generally workable, with some weather to plan around.
September in Decatur averages a daily high of 28.2°C with nights around 17.8°C. Expect roughly 6.7 wet days totalling 98.8mm. Comfortable conditions for being outdoors all day.
October in Decatur averages a daily high of 23°C with nights around 11.2°C. Expect roughly 5.8 wet days totalling 75.1mm. Comfortable conditions for being outdoors all day.
November in Decatur averages a daily high of 17.3°C with nights around 5°C. Expect roughly 7.7 wet days totalling 104.1mm. Comfortable conditions for being outdoors all day.
December in Decatur averages a daily high of 12.6°C with nights around 1.8°C. Expect roughly 10.4 wet days totalling 153.3mm. Generally workable, with some weather to plan around.
Each month scores out of 100. It starts at 100 and loses points for daytime highs outside a 20–27°C band, for wet days, and for nights below 2°C. Nothing else is weighted in — no crowd data, no prices, no opinion. Decatur peaks at 88.
Based on 30 years of records, April–May scores highest for comfort in Decatur, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 31.3°C.
December is the wettest, averaging 153.3mm of rain across roughly 10.4 wet days.
January is the coolest month, with average daily highs around 11°C.